U.S. patent number 4,551,978 [Application Number 06/404,449] was granted by the patent office on 1985-11-12 for bimetallic solar engine.
Invention is credited to Louis R. O'Hare.
United States Patent |
4,551,978 |
O'Hare |
November 12, 1985 |
Bimetallic solar engine
Abstract
The motion produced by a temperature change in a bimetallic
element is used as a source of mechanical work energy in a way
similar to the way that the bimetallic strip operates in a
thermostat but in this thermal engine an array of massive
bimetallic strips is repeatedly, alternately heated and cooled by a
draft of air which draws first heated air and then cooled air over
the bimetallic elements to thereby provide a continuous
reciprocating action. In the principal embodiment the required
draft is provided by a solar heated convection column which by
means of valving draws air first from a solar collector and then
from a cooling duct.
Inventors: |
O'Hare; Louis R. (Fort Collins,
CO) |
Family
ID: |
23599649 |
Appl.
No.: |
06/404,449 |
Filed: |
August 2, 1982 |
Current U.S.
Class: |
60/641.13;
60/529; 60/641.8 |
Current CPC
Class: |
F24S
25/00 (20180501); F03G 6/00 (20130101); F03G
7/06 (20130101); F03G 6/045 (20130101); Y02E
10/47 (20130101); Y02E 10/46 (20130101); Y02E
10/465 (20130101) |
Current International
Class: |
F03G
6/04 (20060101); F03G 7/06 (20060101); F03G
6/00 (20060101); F03G 007/02 () |
Field of
Search: |
;60/527,529,530,531,641.11,641.12,641.8,641.13 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Husar; Stephen F.
Claims
I claim:
1. A solar heat engine comprising:
a source of heated air provided by a hot air solar collector,
a source of cool air provided by a finned air duct situated in a
low temperature region,
a thermal energy converter comprising a plurality of thermally
responsive curved bimetallic elements, each of said elements having
both ends attached to moveable sliders which slide along at least
one guide rod, said bimetallic elements being mounted on said at
least one guide rod in a serial manner with one end of the first of
said bimetallic elements being fixed such that heating and cooling
the serially arranged bimetallic elements produces a compound
reciprocable movement, and a drive rod attached to an end opposite
said fixed end so that said reciprocable movement may be coupled to
an external load,
means for supplying alternate drafts of air from said sources of
heated and
cool air across said thermal energy converter comprising a solar
heated thermal convection column connected in fluid flow
communication with one end of said thermal energy converter and a
switching valve in fluid flow communication with the opposite end
of said thermal energy converter, said switching valve alternating
the fluid flow communication between said sources of heated and
cool air and said thermal convection column such that the draft
created in said thermal convection column draws air alternately
from said sources across said thermal energy converter producing a
reciprocating movement in said drive rod.
2. A solar heat engine as set forth in claim 1 in which said
switching valve is operatively connected to said thermal energy
converter in such a manner that the fluid flow of heated and cool
air is switched near the point of maximum travel of said
reciprocating movement.
3. A solar heat engine as set forth in claim 1 in which said
bimetallic elements are U-shaped.
4. A solar heat engine as set forth in claim 1 in which said
bimetallic elements are spirally shaped.
Description
This invention is a type of thermodynamic engine which is capable
of converting heat energy into reciprocating motion. It is an
engine which requires only low temperature differences in order to
operate. In this engine the temperature differences between the
higher temperature of a heat source such as a solar collector and
the lower temperature of a heat sink such as a cooling duct placed
in the earth are first converted into internal temperature
alternations. This is accomplished by means of valving which
alternates a heated and a cooled fluid flow. In turn the
temperature alternations which result from first the heated and
then the cooled fluid flows provide physical expansions and
contractions of metallic elements which are linked together to
provide reciprocating action with significant displacement. The
temperature changes of the bimetallic elements themselves are
provided by moving first the heated and then the cooled fluid
across and in contact with these elements. The motive force
required to move both types of fluid across the elements is
principally the force of an energetic draft produced at the base of
a solar heated convection column. By using a draft in this way this
present invention closely resembles the art of my copending
application called, "Convection Powered Solar Engine" of Ser. No.
184,205, now U.S. Pat. No. 4,453,382, because both this present
invention and that copending application utilize some energy from a
solar powered convection column to provide an energetic draft and
the draft in both cases provides repeated temperature alternations
by first drawing heated air and then by drawing cooled air across
apparatus which convert temperature alternations into physical
reciprocations. However the inventive concepts are different in
that this present invention makes use of a quite different means of
converting the temperature alternations into physical reciprocating
action. In the former art cited the thermal expansion and
contraction of a fluid, acting to provide pressurizations and
depressurizations against a moveable surface, cause the surface to
move in one direction under pressurization of the fluid and then to
move in the opposite direction under depressurization. Whereas in
this present invention the temperature alternations provide the
opening and closing of bimetallic arches or other shapes which take
place when soild materials are directly heated and cooled. This
aspect of the invention closely resembles the prior art of some
thermostatic control devices in which physical motion is produced
by the expansion or the contraction of metallic elements. Just as
some thermostats employ multiple strips of dissimilar metals joined
along their lengths and then formed into a U-shape to provide a
physical movement when heated or cooled so also this invention is
based upon the principle that different metallic plates with
different coefficients of expansion will interact to cause a
bending effect when they are joined together along their lengths.
Especially, when their joined lengths are bent into the shape of
the letter U, then the thermal expansion or contraction of one
metal plate relative to that of the other produces a widening or
narrowing of the opening of the U shape. However, this invention
differs from thermostat art in that the physical movement which is
produced in this way in this present invention is not used to index
temperature nor to move a control device correlative to a certain
specific temperature, but rather here the physical movement is used
as a part of a system of providing continual reciprocating
energy.
Likewise, this invention is to be distinguished from the art of
thermostatic control by its principal objective which is the
utilization of abundant low grade thermal energy. The use of low
grade thermal energy for the provision of physical work energy is
often neglected because the temperature differences between the
energy input into an engine and those leaving the engine are small
and thereby indicate engine inefficiency. Nevertheless, even the
use of an inefficient energy system is useful if the low
temperature energy source is practically a free energy source.
Since low grade, low temperature energy resources such as solar
energy sources are abundant they can be made to provide much useful
work energy for mankind if efficiency considerations are ignored.
This invention seeks to provide an engine which is able to operate
on solar and geothermal energy.
Another object of the invention is to provide an inexpensive, low
technology engine. This object would make available for physical
work the vast resource of low grade energy by providing a simple
engine which could be easily constructed with low technology tools,
skills and materials. This objective would provide for the use of
simple black box solar collectors in conjunction with simple
metalsmithing practice in order to make reciprocating power
available where it is needed to drive a water pump for agricultural
irrigation etc.
The ways in which these objectives are met in the various
embodiments and the advantages are realized can be more clearly
seen by referring to the drawings.
FIG. 1a shows a U-shaped bimetallic channel with bearings on its
ends.
FIG. 1b shows four sliders supporting two shafts.
FIG. 1c shows a U-shaped bimetallic channel with its bearings
supported on shafts connected to sliders.
FIG. 1d shows a bimetallic channel in its open condition, expanded
by temperature elevation.
FIG. 1e shows a heat expanded channel that has moved sets of
sliders apart.
FIG. 2a shows an array of U-shaped channels each in a contracted
condition.
FIG. 2b shows an array of U-shaped channels each in an expanded
condition in which the top sliders are significantly displaced
upwards.
FIG. 3 is a diagram of a heating-cooling system with a solar heated
convection column, a solar collector, a cooler and a housing with
an array of heat expandable channels.
FIG. 4 of the drawings shows a valve switching means to alternately
admit heated and then cooled air to the bimetallic elements.
FIG. 5 shows bimetallic channel shaped elements and sliders and the
manner they are supported on a single shaft.
FIG. 6 shows a temperature alternation system with liquid heater
and coolers and valves for hot and cold fluid flow over expandable
bimetallic elements.
FIG. 7 shows alternate bimetallic shapes which may be used in place
of the U shaped elements.
Referring then to FIG. 1a, the U shaped bimetallic element 1 is
formed from two metal plates, with each plate having a different
coefficient of expansion. The plates are positioned one on top of
the other and with a flat surface of one plate being bonded to a
flat surface of the other plate. While being held in this contact
the plates are bent into the shape of the letter U. In this bending
and according to the principal embodiment, the plate having the
larger thermal coefficient of expansion is positioned on the inside
of the bend and has the smaller bend radius of the two contiguous
plates. In another embodiment the inner plate has a smaller thermal
coefficient of expansion than the outer plate. Metal tubes are
welded to the ends of the plates and these tubes serve as bearings
2 and 3 on which to support 1.
Referring then to FIG. 1b, the four sliders 5,6,7 and 8 are
cylinders to which are attached shaft elements 9,10,11 and 12. The
cylinder sliders 5 and 6 support shaft elements 9 and 10. Shaft
elements 11 and 12 are supported by sliders 7 and 8.
In the FIG. 1c, the bimetallic element of FIG. 1a is shown being
supported on shafts 10 and 11 which are the same as shafts 10 and
11 of FIG. 1b. The sliders in this FIG. 1c are the same as those of
FIG. 1b.
Now in FIG. 1d, the same bimetallic element as the element of FIG.
1a is seen, but in this FIG. 1d the bimetallic element is shown in
its expanded condition. In the principal embodiment this expanded
condition is effected by the heating of the bimetallic element. In
a secondary embodiment the expanded condition is effected by a
cooling of the bimetallic element.
In FIG. 1e the various components are the same as those of FIG. 1c
except that the sliders 5 and 6 are now separated at a greater
distance from sliders 7 and 8 because of the opening condition of
the bimetallic element 1 which is the same as 1 of FIG. 1d.
Referring now to FIG. 2a, the array of U shaped channels
14,15,16,17 and 18 are all similar to the bimetallic element 1 of
FIG. 1. Each element is supported by its own bearings and shafts as
is 1 of FIG. 1. All of the sliders which are shown, namely sliders
21,22,23,24,25 and 26 can slide on guide rods 30 and 31 which are
supported in base stand 32 and a counterpart base stand not shown
because it is behind 18 in a drawing perspective.
Referring now to FIG. 2b, the channels 14,15,16,17 and 18 are the
same as those of FIG. 2a except that their relative positions have
been changed by a temperature change. Each channel has a wider
opening angle. The wider opening angle of each channel combined
with the wider opening angle of each channel beneith it effects an
upward movement of each slider. The sliders of this FIG. 2b are the
same as those of FIG. 2a except that each is displaced upward. The
total upward displacement of the uppermost pair of sliders is the
result of all the upward displacements of the sliders beneith.
Referring to FIG. 3, temperature changes are effected in
temperature alternation chamber 40 when low pressure produced in
exit plenum 41 by a draft at the base of solar heated convection
column 42 causes alternate fluid flows first from the black box
solar collector 44 and then by means of valve 45 from cooling duct
46. The temperature in 40 rises when the draft from 42 draws heated
air from the black box solar collector through 40 and the
temperature decreases in 40 when the draft from 42 draws cool air
from 46 through 40. The sliders 48 on guide pole 49 are displaced
upward by the openings of bimetallic elements 50. As in the
proceeding FIGS. the openings of the U shaped channels are effected
by a temperature change. In the principal embodiment the
temperature elevation causes an opening of the channels and a rise
of the sliders 48. Subsequent cooling then causes a closing of the
channels and a lowering of the sliders. Repeated temperature
alternations produced by repeated cycling of valve 45 provide
repeated reciprocations of sliders 48. The drive rod 51 attached to
the uppermost slider is used to transmit the reciprocating energy
from the sliders to any external reciprocating energy requirement
such as a reciprocating water pump etc. The machines which use
reciprocating energy are not shown as they are understood in the
art. Entry plenum 52 in conjunction with exit plenum 41 provides
for an even flow of both heating and cooling fluid through 40. The
cooling duct 46 is able to provide cool air or other fluid by being
located in a cool place such as a lake or a pond or by being placed
in the earth etc. The solar heated convection column 42 is a
rectangular black box solar collector of the type used for heating
air. It is disposed with its length in an approximately vertical
plane and it has upper and lower openings in order that the air
heated within might rise and flow through the top opening 53 and
thereby produce a draft through the opening at its base. In other
embodiments 42 is cylindrical in shape with a transparent glaze
along its length for approximately half of its circumference and
with a light absorbing surface along its inner length on the other
half of its circumference. The duct 54 provides fluid flow
communication between 42 and 41. It is not intended to limit the
inventive concept to any specific type of bimetallic element. In an
alternate embodiment the cooling of the bimetallic elements opens
the channels and causes the sliders to rise subsequent heating
reverses the action. Alternate heating and cooling of the elements
still produces the desired reciprocating action. Nor is it intended
to limit the inventive concept to a certain given number of
bimetallic elements, since any number may be used in a system of
thermal alternations to provide reciprocating work energy.
Referring now to FIG. 4, most of the elements of this FIG. 4 are
the same as those of FIG. 3. In FIG. 3 the elements 40, 41, 42, 44,
45, 46, 48, 49, 50, 51, 52, 53 and 54 are all respectively the same
as the elements 60, 61, 62, 64, 65, 66, 68, 69, 70, 71, 72, 73 and
74 of FIG. 4. In this FIG. 4 a mechanism is shown for automatic
cyclic of the temperalternation valve 45. When the bimetallic
elements have opened close to their opening limits then lever
operating rod 76 will be close to the limit of its upward travel
thereby pivoting lever 77 to cause the valve control rod 78 to
engage the valve 65 with cog 79. This action will close heating
duct 80 and open cooling duct 81. In the cooling mode, when 76 has
moved downward to a position close to the limits of its downward
travel, then cog 82 will be moved upward to contact 65 and open 80
while closing 81. In this way ducts 80 and 81 will be repeatedly
opened and closed alternately from each other providing alternate
heating and cooling of temperature alternation chamber 60. In the
embodiment in which cooling produces the opening rather than the
closing of the bimetallic elements, then the relative positions of
the heater 64 and the cooler 66 must be interchanged. In this
configuration the duct 80 will be leading to the cooler 66 and 81
to heater 64. Duct 80 will then be closed to prevent further
cooling and 81 opened to initiate heating at the position in upward
travel of 76 as it approaches its limits of upward movement. The
relative positions of this alternate embodiment are not shown as
they are deduced by transposing two of the elements of the
principal embodiment.
Referring to FIG. 5, sliding block 84 is provided with a hole
through its vertical length for sliding on guide pole 85 which is
supported in base stand 86. The bimetallic elements 87 and 88 are
connected to block 84 by means of pins not shown extending through
84 and through the bearings 89 at the ends of 87. Multiple sliding
blocks 90 (which are like sliding block 84) are linked by multiple
bimetallic elements 91 to move actuator cylinder 92 up and down on
guide pole 95 by means of heating and cooling of 91.
Now with reference to FIG. 6, the actuator cylinder 102 is like 92
of FIG. 5 and is caused to reciprocate by bimetallic elements 101
and sliding blocks 100 on guide rod 105. The heating and cooling of
101 is accomplished by the repeated actuating of valve 106 which
admits alternately heated and then cooled liquid first from
hydronic solar collector 107 and then from liquid cooler 108. Both
hot and cold fluids air circulated by means of small pump 109
driven by electric motor 110. The cogs 111 and 112 on 102 engage
valve actuating rod 113 as 102 is completing its stroke in either
direction. Ducts 114 transport heated fluid to and from temperature
alternation chamber 115. Ducts 116 transport cooling fluid to and
from 115.
Referring to FIG. 7, the sliders 5 and 7 are shown in a diagramatic
side view and these are the same as sliders 5 and 7 of FIG. 1c. The
bimetallic element 1 is also the same in this FIG. 7 as the element
1 of FIG. 1c. In place of 1 in this FIG. 7 may be used the multiple
bimetallic element 120 in order to achieve a greater opening of 5
and 7 under the influence of a temperature change. The multiple
bimetallic element 120 is formed by the joining of many single
bimetallic elements at their ends to form a series. The ends of the
elements at the ends of the series are each terminated with a
bearing like the bearings used along the ends of the bimetallic
element 1 in FIG. 1 and are securred to shafts 10 and 11 in the
same way by these bearings. The bimetallic spiral 121 is similar in
design to those used in thermostats except that it is massive. It
is formed from two strips of metal each with a different thermal
coefficient of expansion from the other. The pieces of metal are
joined along their flat surfaces and the resulting bimetallic strip
is bent into the shape of a spiral in such a way that one of the
two dissimilar metals will be always on the inside of the bends of
the spiral and the other of the two metals is on the outside of the
bending as the spiral is formed. A bearing is attached to the
internal end of the spiral spring at right angles to the radii of
the spiral and another bearing is attached to the outer end at the
same angle. The inner bearing is attached to shaft 11 and the outer
bearing to shaft 10. In this alternate embodiment temperature
changes provide contractions and expansions of the spiral and
reciprocations between 5 and 7.
While the source of heat energy is described as solar energy, it is
not intended to limit the inventive concept to the use of solar
energy alone and in other embodiments geothermal heat is used and
the solar collector is replaced by ducting extending into the hot
earth in order to heat air circulating in the ducting. Similarly,
while a principal object of the invention is to provide a passive
system and a solar powered draft is provided to achieve this
objective, nevertheless it is not intended to limit the inventive
concept to the use of a convection powered draft alone, and just as
a liquid pump is described in FIG. 6 by pump 109 so an air pump is
used in another embodiment in place of collector 42 of FIG. 3 to
circulate both heating and cooling air. In this alternate
embodiment for instance a centrifugal air blower or a radial fan is
placed in the fluid flow circuit immediately before the temperature
alternation chamber such as chamber 40 of FIG. 3. In this position
the air blower draws heated air from collector 44 of FIG. 3 during
one period impelling it through chamber 40 and then, when valve 45
changes air flow direction, the air blower draws cooler air through
cooler 46 and impels it through chamber 40. In this way temperature
alternations are provided in 40 to produce the reciprocations of
the elements 50. The blower is not shown.
This engine is also capable of operating on stored energy and
especially on stored solar-thermal energy. During periods of
darkness or of lower solar radiation, a solar heat storage unit is
employed in one embodiment to power the engine. In this embodiment,
in the place of the draft of air being drawn through the solar
black box collector (such as collector 44 of FIG. 3) air is drawn
through a solar storage unit which has been previously heated by
conventional solar storage heating means. The storage unit is not
shown because solar heat storage means are well understood in the
solar art, and the unit would occupy the position that solar
collector 44 occupies in FIG. 3, and the solar heat storage unit
then follows a solar black box collector and is downstream of the
collector in order to be heated by a fluid flow from the
collector.
Throughout the description of the bimetallic elements, the terms
metallic plates and metallic strips are used to describe the
components of the bimetallic elements. These terms are intended to
include metal alloys as well as elemental metals. Thus a bimetallic
element with a heavy strip of brass bonded to a heavy strip of
copper would provide a suitable bimetallic element.
* * * * *